Tube Rolling w/Crack

[tdogzthmn]

thanks for the response blackplate.  I'd rather not mess with the wiring as things sound great already.  The next tube on my list is the 5998 which seems to be the best all-rounder.  Possibly a 7236 if I find one at a decent price.

[grufti]

I used a Sylvania 7236 for a couple of weeks and then switched to a Tung-Sol 5998. The 5998 wins hands down to my ears.

The 7236 was easier to find and cheaper than the 5998, apparently for a reason.

thanks for the response blackplate.  I'd rather not mess with the wiring as things sound great already.  The next tube on my list is the 5998 which seems to be the best all-rounder.  Possibly a 7236 if I find one at a decent price.

[Spinifex]

What modifications would be required to run a 12BH7 or a JJ ECC99 in a Speedball Crack?

[levlhed]

no mod for 12BH7

I don't know about the JJ ECC99, anyone else know?
I see claims that it is the "same pin out" and can be used in some of the same circuits..

EDIT:  link to manuf. spec sheet http://www.jj-electronic.sk/pdf/ECC99.pdf

[Grainger49]

Shouldn't the 12BH7 be added in the list in the OP?  Or is it a drop in replacement?  I looked and it is not a drop in replacement for the 12AU7.

[Dr. Toobz]

Shouldn't the 12BH7 be added in the list in the OP?  Or is it a drop in replacement?  I looked and it is not a drop in replacement for the 12AU7.

I've just added it (and its similar, taller cousin, the E80CC) under a new section - basically, an "it works with the Speedball, but can't vouch for the standard circuit with plate resistors" category.

I think the main difference between the 12BH7 and 12AU7 is the doubling of heater current for the former; otherwise, the differences in Rp, mu, etc. seem to be slight enough as not to make a huge difference in volume or frequency balance (well, at least not with my Sennheiser HD650s). The power transformer seems happy as ever, even with the somewhat higher (+300mA?) total current draw. I'm sure the Speedball has a lot to do with the seemingly effortless change of tubes.

[Grainger49]

That makes sense.  I added a section in the Eros tube list for works with tube socket rewiring.  There are 2 or 3 that have been discussed in that forum.  Paully is using an adapter that was custom made for him to change the socket pin assignments.

[jrihs]

Hello all, I'm new and just ordered the Crack as well as an 57 Hamburg made bugle boy 12au7 d-getter longplate as well as sveral other notable 12au7's to try out.
Then I read this...
Many tube amplifiers use the common 12AU7 and various simular versions such as the 5814, 5963 and 6189 tubes. A lower distortion replacement is the E80CC with slightly different operating parameters and double the filament current requirements. Be careful regarding the installed height of this tube, about equal to a 6BQ5 & taller than 12AU7 tubes. Regarding the higher filament current, make sure your amplifier has the extra current capacity. Most amplifiers have plenty of reserve capacity. One way to view it is a 250va or say 250 watt power transformer will require an additional 1.9 watts per tube. That is a very small percentage increase in power demand on a 250 watt transformer. My example above with regard to power transformer additional loading is only a very rough guide. A small preamp without a power tube output section can overstress the power transformer filament with E80CC tubes. In this case, Brimar 13D5 or CBS Hytron or CBS 5814 or 5814A are your only option for best quality sonics and are far superior to the standard 12AU7. I also read Sylvania early 1950s tall black plate are of superior sonics, but never heard these tubes.
The Amperex E80CC also labeled at times as 6085. Many persons performing a search miss that 6085 only listing and buyers can get a super deal. Various labels of Amperex manufactured tubes are Valvo, Telefunken, Siemens, etc. Another brand is the Tungsram E80CC. Both are great performing tubes. The Amperex produces a warmer midrange and slightly darker high frequencies compared to the Tungsram manufacture. The Tungsram are brighter on the high frequencies and a little cooler regarding the midrange producing accurate sonics without being the least bit sterile sounding in my applications. I truely enjoy either manufacture.

Both brands of tubes are highly recommended and in most cases will greatly outperform the 12AU7 in home entertainment amplifiers. However, a few audiophiles do like the much high distortion of the 12AU7 for whatever reason. (Be advised my guide is more addressing home entertainment amplifiers vs guitar amplifiers for accurate & neutral playback sonics). The 5814 series was actually a redesigned by RCA 12AU7 due to a few complaints of the 12AU7 distortion figures when introduced in the late 1940s. The 12AU7 tube was not meeting some manufactures requirements such as Collins Radio now called Rockwell Collins

Sooo.. Is this right? was it a bad choice to spend big dollars on 12au7's before trying this type? What are the unheralded advantages to the 12au7's that the reviewer above does not define? Also BTW...What gauge hook-up wire in silver and/or copper do I need to order? THANKS

[Doc B.]

That commentary doesn't consider circuit types, operating points, gain structures, etc., nor does he talk about tuning the tube sound to the rest of the gear in the system. There are other tubes to consider like the 12BH7. And a typical 5814 is not superior to the likes of Mullard CV4003 or Telefunken ECC82 to this old manufacturer's ears.

Just like your nose, when it comes to tubes you have to pick your own to get the utmost satisfaction.

[Grainger49]

jrihs,

There is no thread here for the drop in equivalents for Crack.  I posted a list in the Legacy forum for the FP 1 and FP 2.  They use the 12AU7.  This is that thread:

http://www.bottlehead.com/smf/index.php/topic,1027.0.html

Of course Crack has a 6080 tube also.  I don't have one so I didn't post for it.  I think that most of the

In the FP 2 I have found the Mullard CV4003 to be top notch and really enjoy the Sylvania JAN 6189W/WA.  

But each tube might appeal to different tastes.

YMMV

[tdogzthmn]

What would be a good tube configuration for lower impedance headphones?  I'm interested in buying some grados and would like them to sound their best on my Crack + speedball.

[ToolGuyFred]

First post here - thought I'd share my tube rolling crack experience.

Original tubes supplied were a GE 12AS7G and what I assume is a 12AU7 (couldn't read the writing on the glass). The amp has the speedball upgrade and smaller output caps (220uF Black Gates) which seem OK with my old Sennheiser HD580s.

I had an irritating intermittent hum and low level buzz which sometimes went away when I tapped the chassis plate with a finger. Tapping the chassis plate was clearly audible through the cans so something was obviously very microphonic. Quick visual double check of build and voltages suggested all OK there so time to try different tubes.

First up was a NOS Mullard 6080. Not as pretty as the coke-bottle GE but what an improvement in sound! All microphonics gone, no buzz, no hum, quiet background. Images are more solid, sound is cleaner at all frequencies. A splendid purchase for ten quid (that's UK pounds).

Next in was a NOS Brimar 12BH7. Nothing like the improvement from the 6080 (which is counter-intuitive, I know) but worthwhile all the same. This was twice the price of the 6080.

I also have a second GE 12AS7G (but a parallel shaped envelope, not the coke-bottle style) which I haven't tried yet (once I got the above improvements, I settled down with the music...). Will post again when I've tried it.

[Grainger49]

Since this is your first post I don't know if this is your first kit, so bear with me.  I am only trying to help with your problems with the Crack.

. . .   smaller output caps (220uF Black Gates) which seem OK with my old Sennheiser HD580s.

I don't have much experience with such high dollar caps.  I have used them once but it took weeks for them to break in.  I wondered if you had, or are having the same experience?

I had an irritating intermittent hum and low level buzz which sometimes went away when I tapped the chassis plate with a finger. Tapping the chassis plate was clearly audible through the cans so something was obviously very microphonic. Quick visual double check of build and voltages suggested all OK there so time to try different tubes.

This brings to mind an old vaudeville routine, "Doc, it hurts when I do this..."  So don't tap the top plate.  Microphonics are a tube problem.  You don't get the best quality tube with the kits, Doc et al leave that up to us to play with. 

The buzz being intermittent would normally point to a bad connection, cold solder joint.  Rewet as many solder joints as you can find.  If it is in one channel then it is after the power supply.  If in both it is most likely in the power supply.

[ToolGuyFred]

Since this is your first post I don't know if this is your first kit, so bear with me.  I am only trying to help with your problems with the Crack.

Many thanks. Not my first kit (all suggestions welcome, though). Have been building S/S gear over 30 years. First tube kit was a (now much tweaked) parasex back in the 90's.

. . .   smaller output caps (220uF Black Gates) which seem OK with my old Sennheiser HD580s.

I don't have much experience with such high dollar caps.  I have used them once but it took weeks for them to break in.  I wondered if you had, or are having the same experience?

They do sound better after a few hundred hours but they sound good straight away and then get better. They don't like to be powered down for a long time though, so don't bother with them if you leave your gear switched off for weeks at a time (my stuff is used every day).

I had an irritating intermittent hum and low level buzz which sometimes went away when I tapped the chassis plate with a finger. Tapping the chassis plate was clearly audible through the cans so something was obviously very microphonic. Quick visual double check of build and voltages suggested all OK there so time to try different tubes.

This brings to mind an old vaudeville routine, "Doc, it hurts when I do this..."  So don't tap the top plate.  Microphonics are a tube problem.  You don't get the best quality tube with the kits, Doc et al leave that up to us to play with. 

The buzz being intermittent would normally point to a bad connection, cold solder joint.  Rewet as many solder joints as you can find.  If it is in one channel then it is after the power supply.  If in both it is most likely in the power supply.

One channel, all joints looked good. Still suspect the tube as it went away with the tube swap but time will tell...
Thanks again for your suggestions and interest.

[Grainger49]

Ok!  You have been at it a long time, me too! 

Sounds like the tube swap may have made the difference. 

I have my Black Gates in a GainClone that doesn't have a power switch.  I'm burning in some Teflon Kommie Kaps on it right now.  But I do listen to it because the GC is my work room system.